Luman Elizabeth T, Worku Alemayehu, Berhane Yemane, Martin Rebecca, Cairns Lisa
Global Immunization Division, National Immunization Program, U.S. Centers for Disease Control and Prevention, 1600 Clifton Road NE, Atlanta, GA 30333, USA.
Int J Epidemiol. 2007 Jun;36(3):633-41. doi: 10.1093/ije/dym025. Epub 2007 Apr 9.
Measuring vaccination coverage permits evaluation and appropriate targeting of vaccination services. The cluster survey methodology developed by the World Health Organization, known as the 'Expanded Program on Immunization (EPI) methodology', has been used worldwide to assess vaccination coverage; however, the manner in which households are selected has been criticized by survey statisticians as lacking methodological rigor and introducing bias.
Thirty clusters were selected from an urban (Ambo) and a rural (Yaya-Gulelena D/Libanos) district of Ethiopia; vaccination coverage surveys were conducted using both EPI sampling and systematic random sampling (SystRS) of households. Chi-square tests were used to compare results from the two methodologies; relative feasibility of the sampling methodologies was assessed.
Vaccination coverage from a recent measles campaign among children aged 6 months through 14 years was high: 95% in Ambo (both methodologies), 91 and 94% (SystRS and EPI sampling, respectively, P-value = 0.05) in Yaya-Gulelena D/Libanos. Coverage with routine vaccinations among children aged 12-23 months was <20% in both districts; in Ambo, EPI sampling produced consistently higher estimates of routine coverage than SystRS. Differences between the two methods were found in demographic characteristics and recent health histories. Average time required to complete a cluster was 16h for EPI sampling and 17 h for SystRS; total cost was equivalent. Interviewers reported slightly more difficulty conducting SystRS.
Because of the methodological advantages and demonstrated feasibility, SystRS would be preferred to EPI sampling in most situations. Validating results in additional settings is recommended.
测量疫苗接种覆盖率有助于评估疫苗接种服务并进行合理的目标定位。世界卫生组织制定的整群抽样调查方法，即“扩大免疫规划（EPI）方法”，已在全球范围内用于评估疫苗接种覆盖率；然而，调查统计学家批评选择家庭的方式缺乏方法上的严谨性并会引入偏差。
从埃塞俄比亚的一个城市地区（安博）和一个农村地区（亚亚-古莱莱纳·德/利巴诺斯）选取了30个群组；采用EPI抽样和家庭系统随机抽样（SystRS）进行疫苗接种覆盖率调查。使用卡方检验比较两种方法的结果；评估抽样方法的相对可行性。
最近一次针对6个月至14岁儿童的麻疹疫苗接种活动的覆盖率很高：在安博为95%（两种方法），在亚亚-古莱莱纳·德/利巴诺斯为91%和94%（分别为SystRS和EPI抽样，P值 = 0.05）。两个地区12至23个月儿童的常规疫苗接种覆盖率均<20%；在安博，EPI抽样得出的常规疫苗接种覆盖率估计值始终高于SystRS。在人口特征和近期健康史方面发现了两种方法之间的差异。完成一个群组的平均时间，EPI抽样为16小时，SystRS为17小时；总成本相当。访谈者报告说进行SystRS的难度略大。
由于方法上的优势和已证明的可行性，在大多数情况下，SystRS比EPI抽样更可取。建议在其他环境中验证结果。
